An example of an on-ground tank configured to contain and store an LNG is shown in FIG. 89. An LNG tank 100 shown in FIG. 89 includes a dike 20 disposed on a bottom slab 5, which is supported by piles 4 in the ground 7, and also includes an inner tank 3a and an outer tank 3b, which are made from metallic plates and other components and disposed inside the dike. The LNG is stored in the inner tank 3a, and the spacing between the inner tank 3a and the outer tank 3b is used to maintain the LNG in a cold condition. A side wall portion 31b of the outer tank 3b is disposed along the dike 20.
The dike 20 is provided to prevent liquid leakage and spill of the LNG to the outside even if the inner tank 3a and the outer tank 3b are damaged and/or broken. The dike 20 is configured to withstand the liquid pressure of the LNG even in a low temperature environment. Thus, prestress is applied to the dike 20 by tension members (not shown) disposed in the vertical direction and the circumferential direction of the dike 20.
When an LNG tank is built up, the construction of an inner facility (e.g., the inner tank and the outer tank) starts upon finishing the construction of the dike to a certain height. Thus, the reduction in a construction period of the dike in an initial stage of a construction work has a great impact to a period of the entire construction work. In view of this, an example of building up the dike with precast members is described in Patent Literature Document 1.
In the example of Patent Literature Document 1, a ring base and a wall body are united in a precast block, and a plurality of precast blocks are arranged circularly at predetermined intervals along an outer circumferential line of a tank. Concrete is then poured and disposed between the precast blocks at a construction site for connection and closing/sealing, thereby constructing a lower wall body of the dike.
An example of a joining structure for joining upper and lower precast blocks to each other is shown in FIG. 90. In the example of FIG. 90, each of the upper and lower precast blocks 200 is provided with coupling joints 201, which have fixing elements. The upper and lower precast blocks 200 are arranged such that the respective coupling joints are lapped, a formwork (mold) 300 is disposed, and concrete 400 is poured and disposed between the precast blocks 200, thereby forming a masonry joint between the precast blocks 200.
Patent Literature Document 2 describes that one precast block has a reinforcing steel rod embedded therein and a reinforcing steel rod receiving hole formed therein, the reinforcing steel rod receiving hole of this precast block receives a reinforcing steel rod protruding from another precast block, and grout is poured between the precast blocks to form a joining structure that has the lapped reinforcing steel rods of the two precast blocks.
Patent Literature Document 3 describes a building that has a party wall made from precast walls. The party wall is built up by placing an upper precast wall on a lower precast wall. A U-shaped hook is partly embedded in the lower precast wall beforehand such that the hook is exposed and extends upward, and another U-shaped hook is partly embedded in the upper precast wall beforehand such that the hook is exposed and extends downward. A slab is provided on the lower precast wall, and the upper precast wall is stacked on the lower precast wall with a flattening mortar layer being interposed between the precast walls, thereby joining the precast walls to each other. The U-shaped hooks of the precast walls are arranged such that the U-shaped hooks overlap in the horizontal direction in a recess formed in the upper precast beforehand. A rod-like member is inserted through the respective hooks, and then mortar is loaded into the recess to fix the U-shaped hooks and the rod-like member.
Patent Literature Document 4 describes a joining structure for joining a pair of reinforced concrete structures that face each other. One of the two facing reinforced concrete structures has a protruding reinforcing steel rod protruding from an end face thereof and a spiral sheath pipe receiving hole, and the other of the two facing reinforced concrete structures has a spiral sheath pipe. This joining structure allows the protruding reinforcing steel rod to be inserted in the spiral sheath pipe and an approximately half of the spiral sheath pipe to be inserted in the spiral sheath pipe receiving hole. With this condition, the grout is loaded around the protruding reinforcing steel rod, which is inserted in the spiral sheath pipe, and cured to provide the joining structure.